Sprout Social finds most merchants fail to respond to consumer questions on Facebook and Twitter, a problem compounded during the holiday shopping season when the volume of requests increases.

Ignoring your customers is a cardinal sin of business. Yet that’s exactly what a large majority of retailers are doing on social media, according to a new Sprout Social study.

The stats from the Spout Social’s Q4 2015 Index are damning. Retailers failed to respond to more than 80 percent of consumer questions and requests on social media in the last year. And the cold shoulder from merchants was coldest when you’d think they could least afford it, during the holiday shopping season. During the fourth quarter of 2014, only 16.35 percent of customer queries to retailers were answered.

Compounding the issue is the fact that consumers are more demanding during the run-up to the holidays. Last year, there was a 21-percent increase in the number of inbound social media messages to retailers from the third quarter to the fourth. Sprout Social expects the same this year, predicting that the average retailer will get more than 1,500 messages on Facebook and Twitter during the holiday season. And if last year’s response trends stay the same, five of every six of those messages will be ignored.

Even retailers that regularly answer questions on social media struggle with the concept. People expect quick answers — one of the reasons why they turn to social media — but the average response time for retailers in the Sprout Social Index is 12 hours.

It’s not that these companies are inactive on social media. It’s just that they are mostly acting like a megaphone. During the third quarter of 2015, retailers sent three times more promotional messages than replies.

Retailers would be wise to be more responsive, Sprout Social said, noting another study that found people are seven times more likely to respond to promotions after a brand interacts with them in a meaningful way.

“Social media is an integral part of consumers’ daily lives and a critical communication channel for brands to engage in conversation with their customers during the holidays,” Sprout Social CMO Scott Brandt said in a release. “Whether answering a product question or confirming a customer’s gift order, brands have an opportunity to positively influence awareness, customer loyalty, positive sentiment and seasonal sales through social media engagement.”

Sprout Social also found some interesting results comparing merchants’ use of Facebook and Twitter. Retailers in the study received seven percent more requests on Facebook than on Twitter in the third quarter. As the chart below shows, it’s the first time requests on the social network exceeded Twitter:

Merchants don’t seem to be reacting to the shift. They sent out 114 percent more messages on Twitter in the last six months, outpacing the 100-percent increase on Facebook:

Sprout Social’s recommendation? “It’s worth taking a deeper look at customer service on Facebook since it is generally where people are seeking answers from retailers. Bottom line: You should be able to improve your response rates and times if you understand where people are reaching out to your brand in the greatest numbers.”

There was one semi-positive finding for retailers in the study, which was based on data from 119,000 public social profiles (64K on Facebook and 55K on Twitter) of global businesses. Merchants’ response rates were better than most. The overall rate of response in the 15 industry categories Sprout Social tracks was 11 percent, and retail was second only to utilities.